Laser based scanned beam display systems typically are capable of providing infinite focus of the projected image. Infinite focus means that as the projector is moved farther away from the projection surface, the expansion of the laser beam does not exceed the expansion of the pixel, thereby maintaining the projected image in focus. A scanned beam display may exhibit some distortion in the projected image due to transformation of the image from the spherical coordinates of the scanning platform via scanning at a single point to the rectangular coordinates of the planar projection surface. This type of scanning distortion is sometimes referred to as smile distortion. Typically, such scanning distortion may be corrected via correction optics disposed in the beam path after the scanner. However, placing distortion correction optics after the scanning platform may adversely affect the infinite focus properties of the projector. Furthermore, optics placed after the scanning platform may also cause stray light image artifacts. Distortion correcting optics could be placed prior to the scanning platform, however smaller form factors of the projector may be achieved with post scanning platform optics. In addition, post scanning platform optics may achieve other objectives such as optical sine compensation versus electronic sine compensation.
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